1. Field of the Invention
This invention concerns a method for the chemical modification of a surface based on the reaction of photolytically generated reactive intermediates derived from azido heterocycles with said surface.
2. Technical Background
Various methods for modification of surfaces are known. Radiation-induced grafting of moieties to polymeric surfaces has been disclosed. In some of these prior art processes, multiple stages are involved and reproducability may be a problem.
F. Yamamoto et al., Journal of Polymer Science: Polymer Chemistry edition, Vol 16, 1897-1907 (1978), discuss the grafting of methyl acrylate onto the surface of polyethylene film under the influence of high energy electrons.
He Mingbo et al., Polymer Degradation and Stability, 18, 321-328(1987) discuss the grafting of 2,2,6,6-tetramethyl-4-piperidinyl-methacrylate onto the surface of polypropylene under the influence of ultraviolet radiation.
A. Hult et al, Macromolecules 18, 1804-1809(1985), disclose a method for the surface modification of polymers that is based upon photoinitiated cationic polymerization under the influence of ultraviolet radiation.
Lednicer et al. U.S. Pat. No. 3,954,583 disclose a process for coating materials which are susceptible to interaction with an aromatic sulfonyl nitrene which involves contacting an aromatic sulfonylazide with said material and irradiating. The types of radiation employed are said to include ultraviolet, ultrasound and X-ray radiation.
E. W. Meijer et al., J. Am. Chem. Soc., 110, 7209-7210(1988), discuss the ultraviolet light induced polymerization of phenyl azide and a series of substituted phenyl azides. He proposes a reaction mechanism involving formation of a nitrene followed by a ring expanding nitrene insertion reaction to form a seven-membered ring compound (an azepine), which then polymerizes. The polymerization can be carried out in an image wise fashion if the irradiation is performed through a photomask. There is no indication nor suggestion that azides other than phenyl azides, least of all heterocyclic azides, would react and polymerize in a similar fashion. There is no indication nor suggestion that surfaces other than silica might be suitable substrates for the formation of photopolymerized phenyl azide films.
Reiner et al., U.S. Pat. No. 4,309,453 disclose a process for the covalent surface modification of a macromolecular substance comprising applying a solution of an organic monomeric compound having a hydrophobic linear chain having at least one azide or diazo group at one end of said monomeric compound and having at least one hydrophilic, hydrophobic, oleophobic and/or ionic group at the other end of said compound, to the surface and then photochemically activating said molecule to convert said compound to a nitrene or a carbene. One of the compounds specifically disclosed is a para substituted alkyl phenyl azide. There is no indication nor suggestion that azides other than alkyl azides and the disclosed phenyl azide, least of all heterocyclic azides, would react in a similar fashion.
It is known in the art that different classes of azides, for example heterocyclic azides, may undergo different types of reactions. Different yields of the various types of possible products are obtained. See, Azides and Nitrenes, E. F. V. Scriven, Editor, Academic Press, 1984.